(1) Field of the Invention
The present invention relates to a structured shelf suitable in a case in which a plurality of shelves respectively connected to a plurality of cables, for example, having limitations on bending radius are accommodated in one rack, and more particularly to a structured shelf suitable in a case in which a plurality of line accommodating units respectively connected to a plurality of optical cables having limitations on allowable bending radius are stored in one rack provided in a transmission station.
(2) Description of the Related Art
In general, a transmission signal such as optical signal or electric signal is wire-transmitted in a state where a plurality of transmission cables, such as optical cables or electric cables, or transmission mediums are collectively hardwired in a transmission station (which will be referred to hereinafter as a station or node; for example, transmission terminal station, repeating station, reception terminal station, and other stations) or in a transmission apparatus. An optical cable can provide high-quality transmission, transmission stability, large-capacity data transmission and long-distance transmission, and each station in an optical transmission network carries out interface processing on each of optical signals, packet signals and other signals. Concretely, it carries out optical signal processing, termination processing, transfer processing, format conversion, and others. Each of the functions for these interface processing is implemented in one or a plurality of shelves (for example, line accommodating units). Moreover, each of the plurality of shelves are accommodated in a state fixed by several columns constituting a rack (frame, unit frame). In this sense, the shelf is referred to as a rack-mounted shelf.
In addition, in each shelf, m1 slots permitting the insertion of m1 (m1 denotes a natural number) board units are placed in an equally spaced condition. Each of the board units is equipped with one printed board (printed-circuit board) for the storage of m2 (m2 depicts a natural number) subscriber's lines, and m3 (m3 represents a natural number smaller than m1) board units are detachably inserted into each slot. Thus, the number of shelves to be accommodated is increased/decreased in accordance with an increase/decrease in the number of subscribers.
Still additionally, in general, since a rack is located in a hired portion of a floor of a station, there is a need to reduce the occupying area of a bottom surface of the rack. For this reason, in many cases, a plurality of shelves are stored in a rack in a state arranged in a line. Yet additionally, for increasing the number of shelves (mounting density) storable in one rack, there is a need to achieve the size reduction of the rack and the shelf since limitation is imposed on the vertical width of each shelf. The size of the rack, the diametrical size of a fixing bolt for the shelves to be mounted on the rack and the location spacing between the positions of bolts and between the shelves have been determined according to the engineering specifications such as JIS (Japanese Industrial Standards) and EIA (Electronic Industries Alliance: U.S. Electronic Industrial society), and in the columns of the rack, bolt-fixing holes are previously made at an interval standardized.
FIG. 15 is a front perspective view showing a common shelf, and shows a front surface (surface a) of the shelf. In FIG. 15, a shelf 100 is for conducting interface processing on k (k designates a natural number; for example, k=4) optical cables concentrated, and it includes access panel units (access panels) 110, 111, 120, 130, 140, units A, B for generating cooling air to cool the shelf 100, an extra-portion handling panel 200 for looping extra portions of optical cables 9, and a cable support (cable supporting tool) 250 for maintaining the optical cables 9, connected to the access panel units 110, 120, 130 and 140, in a substantially horizontal condition. In this case, the cable extra portion signifies an unnecessary or redundant portion of the overall length of the optical cable 9.
Each of the access panel units 110 to 140 internally stores a printed board connected to one optical cable 9 for, for example, terminating an optical signal, a packet signal or the like, and carries out the collective hardwiring, repeating and others. Each of the access panel units 110 to 140 has, as one example, a box-like configuration and has a thickness small in vertical directions and further has a depth almost equal to the depth of an armored body (for example, metal body) of the shelf 100. Moreover, each of the access panel units 110 to 140 is inserted into a socket (or slot) of a back board placed on a back surface side in the interior of the shelf 100 so that electric connections are made between the access panel units 110 to 140. The horizontal length (width) of the access panel units 110 and 111 are half the horizontal length of the access panel units 120 to 140. The manufacturer of the shelf 100 designs or changes the size of the shelf 100 to be accommodated in a rack according to the above-mentioned engineering specifications for the rack. The shelf 100 shown in FIG. 15 mixedly stores two types of access panel units having different horizontal lengths.
Furthermore, in each of the units A and B in FIG. 15, for example, three cooling fans are disposed in an up-and-down direction (vertical direction) on the back side of a front panel to generate cooling air for cooling the access panel units 110 to 140.
The extra-portion handling panel 200 is made such that, for example, the three optical cables 9 connected to the access panel units 120 to 140 are wound thereon and the wound optical cables 9 are fixedly secured onto a front surface thereof. The vertical length of this extra-portion handling panel 200 is added to the vertical length of one shelf 100, and the vertical length after the addition is handled as a vertical length of an extra-portion handling area. The optical cables 9 from the access panel units 120 to 140 on the unit B side are disposed to suspend downwardly for avoiding the intersections with the unit B before connected to the extra-portion handling panel 200.
The four optical cables 9 supported by the cable support 250 are wired so as to cross in front of the units A, B, and are connected to the access panel units 110, 111, 120, 130 and 140 in a state located to intersect with the surfaces a, b of the units A, B. Moreover, the optical cables 9 supported by the uppermost portion of the cable support 250 are branched and the optical cable 9 at the uppermost portion thereof after branched pass through an outer frame of the shelf body to be connected to the access panel unit 111 so as to avoid a front portion of the access panel unit 110.
With respect to the cable extra-portion handling, various techniques have been proposed so far (for example, Japanese Patent No. 2909803 and Japanese Patent Laid-Open No. 2000-147269).
Japanese Patent No. 2909803 discloses a subrack having, on its upper surface, an optical connector accommodating box composed of an optical fiber holding section for holding an optical fiber in a state connected to an optical connector and wound and an optical connector holding section for holding a plurality of optical connectors in a state arranged in line wherein, when the optical connector holding section is drawn out in a sliding manner, it rotates around a rear end portion of the optical connector holding section to incline.
This facilitates the removal and accommodation of an optical connector even in a small space. Moreover, since an extra optical fiber portion is held in a state wound on the optical fiber holding section, even in a case in which the distance from an external unit is short, the optical fiber is easily retainable.
On the other hand, in an electronic apparatus disclosed in Japanese Patent Laid-Open No. 2000-147269, an optical connector connecting section for the connection of an optical connector of an external optical fiber is disposed on an apparatus front surface side in an inclination direction of a plane so that the optical connector is detachable in the inclination direction from the apparatus front surface side with respect to the optical connector connecting section.
However, each of the four optical cables 9 respectively connected to the access panel units 110 to 140 (see FIG. 15) passes by the front surface of the unit A and intersects with the drawing direction of the unit A. Accordingly, difficulty is encountered in drawing out the unit A from the shelf 100.
Although it can be considered that the four optical cables 9 take a roundabout route so as not to intersect with the drawing direction of the unit A, this is difficult because there are the limitations on the bending radius of the optical cables 9.
This is because, when the optical cable 9 takes an upward or downward roundabout route with respect to the shelf 100, the vertical occupying range of the shelf 100 increases, which decreases the number of shelves to be mounted in one rack. Moreover, a method of shortening the roundabout route length is unemployable because the bending radius of the optical cable 9 becomes smaller than the allowable bending radius (for example, R30).
In addition, a roundabout route of the optical cable 9 in the drawing direction of the unit A is also unemployable because the bending radius becomes smaller at the U-turn portion of the optical cable 9. Still additionally, it is unemployable because, when the optical cable 9 is led onto a surface of the extra-portion handling panel 200, difficulty is experienced in inserting the access panel units 120 to 140 in an upside direction of the extra-portion handling panel 200.
Therefore, the method of using a roundabout route extremely reduces the shelf mounting density per rack and makes it difficult to set the bending radius of the optical cable 9 at a value below the allowable bending radius, thereby extremely lowering the degree of freedom on wiring.
Still additionally, the method of using the extra-portion handling area requires an extra-portion handling operation for each shelf 100, which makes it difficult to efficiently mount a plurality of shelves 100 in one rack, thus leading to a disadvantage in terms of mounting density per rack.
Yet additionally, when the units A and B are forcibly drawn out from the shelf 100, difficulty is experienced in exhibiting the performance of the optical cable 9 sufficiently.
Moreover, the laying of the optical cable 9 requires an extremely special devices and a repairing operation asks an operator for a high skill and, hence, a quick repairing operation becomes difficult and a high repairing cost becomes necessary, which can result in the suspension of operations of the optical transmission network.
Still moreover, also in audio/visual equipment, the wiring of signal cables can intersect with other units such as amplifier and media player. This also suffer problems similar to those mentioned above.